1. Field of the Invention
The invention pertains to a damping valve for a shock absorber including a valve body with at least one flow-through channel with an outlet covered by an elastic valve disk which is pretensioned, against the body by a spring.
2. Description of the Related Art
DE 44 10 996, to which U.S. Pat. No. 5,615,756 corresponds, describes a flat piston for a shock absorber. This flat piston can be equipped with various valve disks and spring sets, so that a certain damping force characteristic can be obtained.
Thus, in variant V2 of FIG. 1, a valve disk which is clamped rigidly in place around its inside diameter is used. It is also possible to use additional valve disks, the outside diameters of which become smaller with increasing axial distance. The overall valve disk assembly is pretensioned by a cup spring.
A valve assembly of this type represents a compromise between the fatigue strength of the valve disks and the desired damping force characteristic. In many cases, the goal is to obtain a weak damping force when the flow velocities in the damping valve are low; this is accomplished with a xe2x80x9csoftxe2x80x9d valve disk. At very high flow velocities, however, a very soft valve disk would either break or undergo plastic deformation. The fatigue behavior is also strongly dependent on the material.
It is also obvious that it would be possible to choose a valve disk made of thicker material, but in this case, it is no longer possible in some cases to obtain the desired low damping forces at low flow velocities.
The object of the present invention is to create a damping valve which, first, provides a low damping force at low flow velocities and, second, has high fatigue strength even at high flow velocities.
The task is accomplished by providing at least one support disk of smaller diameter, which does not execute any elastic movement, on the elastic valve disk, facing the spring, the spring acting radially outside the support disk.
With respect to the valve disk, the minimum of one support disk has the effect of reducing the internal stresses in the valve disk caused by the deformations under the flow arriving from the flow-through channel to a level significantly below that known in the state of the art. This means that a valve disk with a greater degree of overall elasticity can be used, so that weaker damping forces can be realized.
Depending on the desired damping valve characteristic and the amount of radial space available, it is also possible to use several support disks, the diameters of which increase with increasing distance from the valve disk. The support disks can be very thin, because they are not required to execute any elastic motion. The valve disk rests against the outer edges of the support disks. The stress level reached in the valve disk can be controlled very accurately by the way in which the individual support disks are stacked with respect to their diameters and thicknesses.
Especially when only a very few support disks are used, it is appropriate for the largest support disk to be rigid. Otherwise, it is possible under certain circumstances for the very thin support disks to undergo elastic deformation as well during the elastic deformation of the valve disk.
Alternatively or in combination, it is also possible to use a rigid support disk which has a convex surface facing the valve disk. This possibility is especially attractive when the large numbers of parts are to be manufactured.
With respect to the construction space available, the spring is designed as a cup spring.
So that a wider range of variation is possible with respect to the coordination and selection of the springs, at least one compensating disk is provided on the valve disk, in the radially outside area, concentrically to the minimum of one support disk. The spring is supported on this compensating disk. It is possible with one and the same spring, for example, to pretension the valve disk to different degrees by varying the thickness of the compensating disk or possibly several compensating disks.
The compensating disk can be guided reliably by centering it on the minimum of one support disk. Alternatively, the compensating disk can position itself radially by a centering surface of the piston. The advantage of this variant is that the outside diameter of the support disk can be selected independently of the inside diameter of the compensating disk and thus the optimal support points for the valve disk can be obtained.
So that no additional stress peaks in the valve disk are produced, the diameters of the compensating disk are selected in such a way that it is aligned with the valve contact surface for the valve disk, at least in the axial direction.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.